Variable resistance phonograph pickup and system



y 1949. w. ECKHARDT ET AL 2,476,848

VARIABLE RESISTANCE PHONOGRAPH PICKUP AND SYSTEM Filed July 5, 1945 2Sheets-Sheet 1 INVENTORS WALTER LECKHARDT MADISON CAWEIN ATTORNEY July19, 1949. w. ECKHARDT ET AL 2,476,848

VARIABLE RESISTANCE PHONOGRAPH PICKUP AND SYSTEM Filed July 5, 1945 2Sheets-Sheet 2 INVENTOR WALTER L. ECKHARDT MADISON CAWEIN ATTORNEYPatented July 19, 1949 VARIABLE RESISTANCE PHONOGRAPH PICKUP AND SYSTEMWalter L. Eckhardt and Madison Gawain, Fort Wayne, Ind., assignors, bymesne assignments, to Farnsworth Research Corporation, a corporation ofIndiana Application July 5, 1945, SerialNo: 603,362

16. Claims. 1

This invention relates generally to phonograph pickup devices and moreparticularly to a phono. graph pickup device adapted to translate sound.

characteristics which make themresonant in a.

portion of the audio frequency band. Toprovide such devices having. arelatively uniform frequency responseover the entire audible frequencyrange entails numerous design problems.

The relatively high mass of suchdevices causes them tdhave a sluggishrespons inthe higher frequencies of the. audible range andpreventsinstantaneous responseof the-stylus to the higher.

frequency vibrations whichare-cut in arecord. This results in arelativechange of phasebetween the low frequency sound signals and thehigh frequency sound signals so that the high frequencieshave a timedelay with respect to the low frequencies. Thus the sound which isreproduced does not have the same. phase relationship between the highand" low frequency components ascompared to the-phase relationshipswhich were established on the record.

The characteristics of conventional pickup'devices such' as thoseenumerated in the foregoing discussion make it particularly difiicult toprovide a pickup device whichis capable of responding to soundrecordings of both the hill and dale type and the lateral cut. type.Ordinarily a pickup device which responds to both types of. recordingsmust necessarily have a relatively higher mass than a pickup which isdesigned to respond to a single type of recording. Thus the quality ofresponse of "a conventional pickup capable. of responding to both typesof recordings is even lower than that of a pickup which is specificallydesigned to respond to a single type of recording.

Accordingly, it is the principal object of this invention to provide aphonograph pickup device having a uniform response characteristic oversubstantially the entire audible frequency band and adapted to translatehill and dale recordings or lateral cut recordings.

A further object of this invention is to provide a phonograph pickupdevice,the mass of which is reducedwith respect to that'of conventionalpickup devices.

A still furtherobject or this invention is; to

2 provide a phonograph pickup deviceof suchmass as to. preserve thephase.relationshipbetween.re-

corded high and: low frequency. components-of a sound signal.

Anotherobject offthis. invention is to provide circuit means forcooperating with a pickup capable oi-v translating recordings of thehill-and daletype; orwof. the lateral cut. type whereby to control theelectrical outputof thedeyice and sea lectivelyi effectv aresponseto oneor the other types of recordings.

' Still another objector this inventionis to provideca circuit. adapted.to convert the pickup device from one'which responds to hill and dalerecordings to. one-which responds to lateral cut recordings. or.vice-versa and at the same. time prevent. amplification of recordingsof. the nonselectedtype.

In accordance with this invention there is provided a phonograph pickupdevice consisting of a flexible means, means for flexing the flexiblemeansandia plurality of'resistance members disposed on theiflexiblemeam'so as to be variable by vertical andhorizontal' flexing or the flexiblemeans.

In accordance with a" further feature of this invention; there isprovided aphonograph pickup device adapted" to reproduce. records. ofthe hill and dale'type' or of the-lateral cut type. This devicecomprises a flexible means having a portion atone end adapted to befixed to a phonograph pickup'arm together with an extended portionhaving a stylus fixed at its free end for fiexingthe' extended portionin response to bill and dale sound tracks orlat'eral out sound tracks.There provided-on the'extended portion of the flexible' -means anelectrically resistive means for effecting" control of an electriccircuit when the extended-portion is'flexed in a' vertical or horizontalplane;

For electrically controlling the output of the phonographipickup' deviceprovided. in accordance'with this invention, there is provided anelectrical circuit consisting of. potential dividers connected'across'certain components of the electrically resistive meansinthe pickupdevice for rendering'certain ones of said components effective forresponding to hill and dale sound tracksandcertain others of saidcomponents ef fective to respond'to' soundtracks of the lateral cuttype;

For a better understanding of. the invention, together'with other andfurther objects thereof; reference is made tov the followingdescription, taken in 'connection" with the accompanying drawings, andits scope will be pointed out in the appended claims:

In the accompanying drawings:

Fig. 1 of the drawings is an elevation of the pickup device provided inaccordance with this invention together with its associated pickup armwhich is shown partially in cross section;

Fig. 2 is a plan bottom view of the device illustrated in Fig. 1;

Fig. 3 is an exploded perspective ofthe pickup device provided inaccordance with this invention;

Fig. 4 is a cross section taken online 4-4 of Fig. 3;

Fig. 5 is a fragmentary cross section of the pickup device taken on line'5-5 of Fig. 4;

Fig. 6 is a circuit diagram illustrating a control circuit provided inaccordance with this invention and incorporating the electricallyresistive means which form a portion of the pickup devices illustratedin Figs. 1-5;

Fig, 7 is a perspective view of a modified form of the pickup deviceillustrated in Fig. 3 with the stylus mounting omitted; and

Fig. 8 is a cross section taken on line 8-8 of Fig-7.

Referring now to Figs. 1, 2 and 3 of the drawings, there is illustrateda preferred modification of this invention consisting of a pickup arm I,a pair of clamping members 3 and 4 fixed to pickup arm I by suitablescrews 6 and 1 together with sound translating pickup l0. Pickup deviceIn includes an enlarged portion l l which is adapted to be clampedbetween elements 3 and 4 by means of screws l2 and |3. Integrally formedwith the enlarged portion ll of pickup element I is an extended portionl to which is attached, in a manner to be described hereinafter, astylus 16 for tracking the groove of a hill and dale type record or alateral cut record.

Pickup element l0 may be formed of any type of insulating material such,for example, as plastics like Celluloid, polystyrene or other materialsof similar flexibility and mass. On the extended portion I 5 of pickupelement H] a number of grooves 18, preferably four, are out which may beof the order of 1 5 inch in depth whereby to provide vertical andhorizontal surfaces on which may be painted or otherwise depositedlayers of electrically resistive material 20, 2|, 22 and 23 such, forexample, as finely divided carbon particles similar to graphite. Thus,there is provided comparatively long strips of electrically resistivematerial. The strips cover the parts of the surface of portion l5located in the quadrants between the vertical and horizontal axes ofportion Hi. When portion is flexed, the contact pressure betweenthecarbon particles changes thereby to change the electrical resistances ofthe strips.

The layers of resistive materials 20, 2|, 22 and 23 are adapted torespond electrically to sound records of either the hill and dale typeor of the lateral cut type. When the extended portion I5 is flexed in avertical direction as in the case of hill and dale records, the carbonparticles along the horizontal surfaces 25 of the strips 20, 2|, 22 and23 are, in effect, moved to vary the contact pressure between adjacentparticles. For example, when portion I5 is flexed downwardly, theparticles on the upper horizontal surfaces tend to separate whereas theparticles on the lower horizontal surfaces tend to move closer to oneanother. On the other hand, when portion I 5 is flexed upwardly thereverse is true.

Thus, the resistance changes in the upper and lower surfaces 25 areequal and opposite and the currents which flow through the resistivestrips may be utilized to operate a push-pull amplifier device as willbe described hereinafter.

When the extended portion [5 is vibrated in a horizontal plane as in thecase of lateral cut records, the vertical surfaces 26 of the resistivestrips are stressed in a manner similar to that described in connectionwith the horizontal surfaces 25. V In a similar manner, there isproduced equal and opposite changes of resistance which may also beutilized to operate a push-pull amplifier device.

In order to provide electrical contact with the resistive strips, theyare continued from extended portion l5 onto the surfaces of enlargedportion H. Thus, for example, resistive strip 2!] is terminatedonenlarged portion 5 i by a conductive coating 28 and resistive strips 2|,22 and are also terminated on enlarged portion H in conductive coatings29, so and 3|, respectively. Clamping member 3 includes fixed terminals33 for engaging conductive coatings 29 and 3|. Clamping member includesas an adjustable clamping portion thereof a terminal strip 35 which isadjustably mounted on member 2 by setscrews 35. Member 35 includesterminals 38 affixed thereto for engaging with conductive coatings 29and 3|. When pickup device It) is initially affixed to clamping members3 and it is placed so that the enlarged portion Ii protrudes between theclamping members with the conductive coatings 28, 29, 30 and 3! injuxtaposition with terminals 33 and 38. Setscrews 36 may then be rotatedto move terminal strip 35 and contact members 38 into engagement withthe conductive coatings to provide intimate electrical contacttherewith. Terminals 33 and 38 may be connected to the exterior ofclamping members 3 and 4 by conductors 40.

For supporting the stylus at the free end of extended portion l5, thereis provided member 42 having a conductive coating 43 which may beclamped to extended portion 5 by means of screws Ml, thereby to providea support for stylus i6 and intimate electrical contact between all ofthe resistive strips 2!], 2|, 22 and 23. For providing an electricalconnection to coating ie, there is a bore 4! (Figs. 4 and 5) withinextended portionl5 through which extends conductor 48. At the free endof enlarged portion N, there is provided a conductive pin 5| to whichconductor ie may be connected and to which may be connected conductivecoatings 52 which are disposed on the outer surface of enlarged portionll. Coatings 52 may be connected to the exterior of clamping members 3and 3 by means of contacts 53 on the clamping members and conductors 54.

Referring to Fig. 6 of the drawings, there is illustrated a circuitadapted to control and amplify the electrical variations produced inconductive strips 20, 2|, 22 and 23. These strips appear in Fig. 6 asresistors indicated by identical reference characters. The member 42(Fig. 3) for joining the ends of the conductive strips, is indicated bythe same reference character in Fig. 6. For providing a means forconverting the pickup device from a hill and dale pickup to a lateralcut pickup, or vice versa, there are provided potentiometers 69, El, 62and 63 which are connected across resistors 2l-20, 20-22, 22-23 and 23-2I, respectively.

The slider 65 of potentiometer 6B and slider 66 of qootentiometerifi I?are. connected to a point 68 icommon'sto resistor 12 :andlpotentiometers :60 andndl Thei point 1'68 ;is also connectedthrough;

conductm: 57' to the cont1ol"grid"of vacuum. tube 10. Point. 68 is alsoconnected -through resistor HiriThe plate resistcrs ia and T! are alsoconthe positive side of the source of potential nected t'o thepos'itiv'e side-of source-l4 and to the.

platesof tube's lfl iand 'll'. The slid'ers Hi and. 8B'tjfpotentiometefs 52 and 63;irespectively', are

connected to the -point fi'i c'ommon to resistor 23 cuitfof -convertingthe pickup device 89 for operatingin con-junction with hill and daletype record grooves or lateral cut record grooves. If it is desiredtoutilize the pickupdevice in conjunetioli withhill and dalerecordgrooves, po-

'25 vither a volume control or a switching cirtentioine'ter slider 65'is moved; to theextreme left position toshort-circuitresistor Gil-whilepo- .7 tentiometer slider 19 is simultaneously movedto its iiextre'met 1rightnposition toL- short-circuit re sistor fi Thustcurront flows from:source 14 through resi'ston iii-through resistors ZU-a-nd 2! I toaground-i and-f also from source :14 through .ree

sister-s13, r22 andi23 toground As the resistance of zthez 'resistorschanges in response to the sound wavesccut :in .thetrecord; avariablepotentials. are

tentiom'ete'rs '6 l ands-5 iv-may;- be :varied to effect avolume-controls;

ln thezcase of laterali cutirecords, potentiometer sliders; ::and:ma'yx-be moved to their. extreme lower andaupper :positions:respectively to} shortcircuituespectively resistors 5i and 63.- Thus thechangesgofresistance efie'cted by la'teralzvibration.-;-.

of "the vpickup.; devicecause --variable potentials to onthegrids-citric tubes Wand H 2 For volume control, :potentio-meters fiiland 62 maybe varied.

Referring to Figs. 7 and 8 of the drawings;.,.

there, is-illustr-ated-aa modification/of the pick? up -.-:levice l G.Illethifi modification, the extended:

portiom- 15;15 provided with rectangular chan-z nelstfifiefil,;92-and--93: wliich .aredisposed-on the verticaland. horizontalaxes of portion I l 5, as best illustrated-in Fig. 8. The channelsare-filled-with a resistance material asin .the preferred modificationtovfornrresistive strips 2G, .2l,.22. and 23..

These-strips are continued to enlargedportion H to form terminalistrips.28, 29., 30, 3!. and 52,.

as.-,in.-th e. preferred modification... Thestylusesupportingtdevice=42Qmay be secured to the free.

end of portion 15 in. the. same manner asrillu'se.

trated in Fig. 3. j

In'ithisfmodification, flexure of portion 15 by a hilland dale recordgroove varies theresistance of,,strips-29and 221 byequal andoppositeamounts similarly to provide a push-pull electrical signal. .Aconventional push-pull amplifier may be utilized to amplify. the signalsand switches may be provid'edifoi' connecting-whichever, strips are de-.sirdtobe effective."

Frd'mothetioregoing; it is .1 evident; .that atherewls y; provided inaccordance with this invention; a

phonograph .-pickup::':device:: 'havingzua substan:

tially Zuniform' frequency response; characteristic and adapted tctranslate :either hilliand dale recordin'gs'or lateralgcut recordings.The; mass of.- this pickup: device is such: that :its: inertia: effectsJ do not prevent H instantaneous; response of the 1- stylus; whereby-allaudiblen frequencies are :re-

produced faithfully? with 11 respect to itheir phase.

While the I drawings: illustrate. the preferred features of thisinvention; "it will be obvious. to those skilled inth'e artthattheinventive con-. cept includes various modifications; For example; the'pickup member c l 0 is illustrated ashavin 7 channels for-receivi'n'gresistance material but it is within the'scope of this invention to-coat the outer surface 'of-the 'pickup member with strips of resistancematerial of a desired thickness whereby-to provide a pickup device whichwill operate in 'the same manner as that illustrated in the drawings.-Itis also. obviousthat various other arrangements of contact stripsmaybe'provided on pickupdeVice-JO such ,--for example; as

foil or rigid metallic' stripss Further, itis not necessary to utilizethe particular type ofclamping members-shown in the drawingses anysuitable mechanicafarrangement falls'within the" scope of thisinventionwWhile there has been-described what, at present;-is considered thepreferred embodiment of the invention; it will-beobvious to thoseskilled in the art that various changesand modifications may be madetherein without departing from the invention, and therefore, it is aimedin'the appended -claims' ;to'-" coverall" such" changes andmodifications as -f all within the true spirit" and scope of theinvention."

What is claimed is:

lpsound' "translationapparatus' comprising flexible means, meansj'iixedthereto for flexing said flexible means; a plurality ;of1channelsdisposed'on said flexiblemeans, certain of said channels comprisingsurfaces disposedat angles to the surfaces" of certain others of'saidchannels and resistive material fixed'tosaidisurfaces.

2. Sound z'translation apparatus. comprising flexible means'y'means'fixed at one end thereof forflexing said; flexible means, a plurality ofchanne'ls'diagonally disposedon the outer surface of said flexiblemeansanol'strips of resistive material fixed to "said surfaces.

3. Sound translation apparatus comprising flexible 'means, meansfixedthereto .forflexing.

said'flexiblemeans, a plurality of channels dis: posed on: saidvflexible means, each channel comprising surfaces disposed at 90 anglesto one. another andstrips'of carbonaceous material fixed to "saidsurfaces;

4. Sound translation apparatus comprising flexible means, means. fixedat one end thereof for flexing' said flexiblejmeans, a plurality ofchannels disposed on the outersurface ofsaid flexible means, eachchannel comprising surfaces disposed-at'90 angles to oneanoth'e'r andstrips of'carbonaceous material fixed to'said surfaces.

5. Sound "translation apparatus comprising flexible means 'havingaportion'at one; end adapted to be fixed to a phonograph pickuparmand-an'extended portion having four' channels spaced fIOllTOI'lG anotheron diagonal'lineswith respectfto the longitudinal axis of said means, astylus fixed -at*the' free'end of said extended portion'for' flexing itin a vertical or horizontal1i plane and electrically resistive materialfixed to the surfaces of said extended portion which define saidchannels.

6. Sound translation apparatus comprising flexible means having aportion at one end} adapted to be fixed to a phonograph pickup arm and areduced portion having four channels spaced from one another anddisposed in the four quadrants defined by the vertical and horizontalaxes of said portion, a stylus fixed at the free end of said extendedportion for flexing it in a vertical or horizontal plane andelectrically resistive material fixed to the surfaces of said extendedportion which define said channels.

7. Sound translation apparatus comprising flexible means having a baseportion at one end adapted to be fixed to a phonograph pickup arm and anextended portion having four channels spaced from one another anddisposed in the four quadrants defined by the vertical and horizontalaxes of said portion, a stylus fixed at the free end of said extendedportion for flexing it in a vertical or horizontal plane andcarbonaceous particles fixed to the surfaces of said extended portionwhich define said channels.

8. Sound translation apparatus comprising flexible means having anenlarged portion at one end adapted to-be fixed to a phonograph pickuparm and an extended portion having four channels spaced from one anotherand disposed in the four quadrants defined by the vertical andhorizontal axes of said portion, electrically resistive means fixed tothe surfaces of said extended portion which define said channels,conductive means secured to the free end of said extended portion incontact with said resistive means, terminal strips on the surface ofsaid enlarged portion some of which are connected to said resistivemeans, a conductor extending from said conductive means through saidextended portion into said enlarged portion and electrically connectingsaid conductive means to one of said terminal strips and a stylus fixedto said conductive means for flexing said extended portion in a verticalor horizontal plane.

9. Sound translation apparatus comprising flexible means having anenlarged portion at one end adapted to be fixed to a phonograph pickuparm and an extended portion having four channels spaced from one anotherand disposed in the four quadrants defined by the vertical andhorizontal axes of said portion, carbonaceous strips fixed to thesurfaces of said extended portion which define said channels, conductivemeans secured to the free end of said extended portion in contact withall of said carbonaceous strips, terminal strips on the surface of saidenlarged portion some of which are connected to said carbonaceousstrips, a conductor extending from said conductive means through saidextended portion into said enlarged portion and electrically connectingsaid conductive means to one of said terminal strips and a stylus fixedto said conductive means for flexing said extended portion in a verticalor horizontal plane.

10. Sound translation apparatus comprising flexible means having aportion at one end adapted to be fixed to a phonograph pickup arm and anextended portion, said extended portion including vertically andhorizontally disposed channels a stylus fixed at the free end of saidextended portion for flexing it in a vertical or horizontal plane andelectrically resistive elements fixed to the surfaces of said channelsin alignment with the vertical and horizontal axes of said extendedportion.

11; Sound translating apparatus comprising flexible means, means fixedthereto for flexing said flexible means, first resistance means disposedon said flexible means so as to be variable by vertical flexing of saidflexible means, second resistance means disposed on said flexible meansso as to be varied by horizontal flexing of said flexible means,amplifier means including an input circuit and voltage dividing meansfor coupling either said first resistance means or said secondresistance means to said amplifier means.

12. A sound-translating circuit comprising electrical pickup meansconsisting of a plurality of resistors adapted to be varied in responseto hill and dale or lateral cut recordings, means for shuntingsuccessive pair of resistors for controlling the response thereof,push-pull amplifier means including a pair of input circuits andconductor means for coupling said shunting means to said input circuits.

13. A sound-translating circuit comprising electrical pickup meansconsisting of a plurality of resistors adapted to be varied in responseto hill and dale or lateral cut recordings, potentiometers connectedacross said resistors for controlling the response of said resistors,push-pull amplifier means including a pair of input circuits, conductormeans for coupling the sliders of one pair of potentiometers to one ofsaid input circuits, conductor means for coupling the sliders of anotherpair of potentiometers to the other of said input circuits and a sourceof potential connected between said amplifier and said potentiometers.

14. A sound-translating circuit comprising electrical pickup meansconsisting of a plurality of resistors adapted to be flexed in responseto hill and dale or lateral cut recordings, means for connecting saidresistors to a common point, potentiometers connected across the freeends of said resistors to form a star connection whereby successivepairs of resistors are shunted by said potentiometers for controllingthe response of said resistors, amplifier means including a pair ofvacuum tube input circuits, means for coupling the sliders of one pairof adjacent potentiometers to one of said input circuits, means forcoupling the sliders of another pair of adjacent potentiometers to theother of said input circuits and a source of potential connected betweensaid common point and points of said star connection between thepotentiometers of each said pair.

15. A sound-translating circuit comprising electrical pickup meansconsisting of a plurality of resistors adapted to be flexed in responseto hill and dale or lateral cut recordings, means for connecting one endof each resistor in common, potentiometers connected across the otherends of said resistors to form a star connection whereby successivepairs of resistors are shunted by said potentiometers for controllingthe reponse of said resistors, push-pull amplifier means including apair of input circuits, means for coupling the sliders of one pair ofadjacent potentiometers to one of said input circuits, means forcoupling the sliders of another pair of adjacent potentiometers to theother of said input circuits and a source of potential connected betweensaid common connecting means and points of said star electrical pickupmeans consisting of a plurality,

of resistors adapted to be flexed by vibration in first and secondplanes in response to the hill and dale or lateral cut recordings, meansfor connecting one end of each resistor to ground, potentiometersconnected across the other ends of said resistors to form a starconnection whereby successive pairs of resistors are shunted by saidpotentiometers for controlling the response of said resistors, push-pullamplifier means including a pair of input circuits, conductor means forcoupling the sliders of one pair of adjacent potentiometers to one ofsaid input circuits, conductor means for coupling the sliders of anotherpair of adjacent potentiometers to the other of said input circuits anda source of potential connected 10 between ground and points of saidstar connection between th potentiometers of each said pair.

WALTER L. ECKHARDT. MADISON CAWEIN.

REFERENCES CITED The following referenlces are of record in the file ofthis patent:

